The invention relates to a fuel pump comprising an electric motor which has a commutator having a plurality of laminates and carbon brushes which slide over the laminates, and which has turns which are electrically connected to individual laminates and are arranged in slots in an armature.
Fuel pumps of this type are frequently used in modern motor vehicles having 12-volt on-board electrical systems and are known in practice. The electric motors of the known fuel pumps are so-called permanently excited, commutator DC motors. In this case, the number of coils corresponds to twice the number of slots in the armature. A stator which surrounds the armature has permanent magnets. A respective end of each of the laminates is connected to two coils. The carbon brushes each make contact with one laminate on opposite sides of the commutator. The fuel pump is usually arranged with the electric motor inside a fuel container, with the result that replacing the carbon brushes involves a very great deal of effort.
One disadvantage of the known fuel pumps is that the service life of the electric motor, particularly in the case of voltages higher than 12 volts, is very limited. For example, the service life of the carbon brushes is reduced by 90% when changing over to a 42-volt on-board electrical system.
A voltage regulator could be connected upstream of the electric motor in order to limit the voltage to 12 volts. However, this leads to great outlay for supplying electrical power to the electric motor.
Furthermore, the number of laminates and thus the number of turns could be multiplied. However, this also leads to great structural outlay on the fuel pump.
The invention is based on the problem of designing a fuel pump of the type mentioned in the introduction in such a way that the longest possible service life of the carbon brushes is ensured, even with voltages higher than 12 volts.